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Checkweighers: A Comparison Of Capacitance And Gravimetric Checkweighers For Capsules
April 23, 2007
•White Paper: Checkweighers: A Comparison Of Capacitance And Gravimetric Checkweighers For Capsules
Today, manufacturers verify capsule weight using equipment that employs either an electronic field (capacitance) or load cells (gravimetrics). If you're considering adding a capsule checkweigher to your operation, you should understand the principles behind each technology and the appropriate application.
Capsule Checkweighing Methods
Capacitance Method
Capsule checkweighers that use an electronic field typically use the capacitance method. In operation, capsules pass through an electronic field created between two parallel plates. As each capsule passes between the plates, it momentarily disturbs the electronic field. The capsule checkweigher reads each disturbance and converts it into a known weight. To enable the machine to determine weight, you must calculate the conversion numbers when you set up the equipment. That's done by establishing the minimum and maximum capsule weights that are acceptable. Next, you select samples of capsules from each extreme of the specified weight range and run them through the capsule checkweigher. The checkweigher then graphs a regression analysis, which enables you to define the statistically acceptable weight range. The capsule checkweigher is now ready for operation, measuring all capsules passing through it against the acceptable minimum and maximum limits. The machine directs individual capsules into "accept" or "reject" bins. A capacitance-type unit typically handles 30 capsules per second.
Gravimetric Method
Load cells are the key components of gravimetric capsule checkweighers. They operate on the principle of magnetic force restoration, also known as electromagnetic power compensation. Essentially, a load cell is a transducer and converts the weight of a capsule into an analog electrical signal. That signal, in turn, is converted into a numerical measurement of weight.
•White Paper: Checkweighers: A Comparison Of Capacitance And Gravimetric Checkweighers For Capsules
